What's the difference between Energy and Strength?

Energy is what you use when you are exploring rooms. Strength is used for friends' visits only.
Energy is used each time you explore a room and you are given 30 energy points when you start the game. Energy tab is located in the top center of your game screen and you can see a clock under it which gives you one energy point each time it hits zero. Each time you level up, the energy limit increases by 10 and your energy restores to maximum. If you run out of energy it will regenerate by one energy point per three minutes. You can obtain energy points in a few ways: let it regenerate over time, activate the relative charms, or you can purchase meals with diamonds in the game Store (Chocolate, Cup of Coffee, English Breakfast, etc.).
Strength is used each time you visit a friend and you are given 25 strength points when you start the game. Each time you level up the maximum strength increases by 10 and you get complete strength tab refill. Each time you give your friend hints you spend 10 strength points. If you run out of strength it will regenerate by one strength point every three minutes. You will not be able to visit friends until you have enough strength points to help them out. You can obtain strength points by waiting until it regenerates by itself, or by using relative items: Expander, Dumbbels, Barbell, etc.